Alloy thin films exhibiting perpendicular magnetic anisotropy

Abstract

A method for forming a CoFeSiB—Pd alloy thin film exhibiting perpendicular magnetic anisotropy includes: simultaneously sputtering a CoFeSiB target and a Pd target inside a vacuum chamber to form a CoFeSiB—Pd alloy thin film on a substrate disposed inside the vacuum chamber; and annealing the substrate, on which the CoFeSiB—Pd alloy thin film is formed, to exhibit perpendicular magnetic anisotropy.

What is claimed is: 
     
       1. A method for forming a CoFeSiB—Pd alloy thin film exhibiting perpendicular magnetic anisotropy, the method comprising:
 simultaneously sputtering a CoFeSiB target and a Pd target inside a vacuum chamber to form a CoFeSiB—Pd alloy thin film of an amorphous structure without exhibiting perpendicular magnetic anisotropy as-deposited on a substrate disposed inside the vacuum chamber; and 
 annealing the substrate, on which the CoFeSiB—Pd alloy thin film of an amorphous structure without exhibiting perpendicular magnetic anisotropy is formed, to change from the amorphous structure to a polycrystalline structure for exhibiting perpendicular magnetic anisotropy; 
 wherein the method further comprises forming a buffer layer before forming the CoFeSiB—Pd alloy thin film and forming a seed layer before forming the buffer layer, wherein the buffer layer is Pd having a thickness of 3 nm or more, wherein a temperature of annealing the substrate, on which the CoFeSiB—Pd alloy thin film is formed, is higher than 300 degrees Celsius and lower than 600 degrees Celsius, and wherein an interdiffusion of Pd elements occurs between the CoFeSiB—Pd alloy thin film and the buffer layer during the annealing. 
 
     
     
       2. The method as set forth in  claim 1 , further comprising:
 forming a capping layer after forming the CoFeSiB—Pd alloy thin film. 
 
     
     
       3. The method as set forth in  claim 1 , wherein the CoFeSiB—Pd alloy thin film is formed by dc sputtering using the CoFeSiB target and the Pd target. 
     
     
       4. The method as set forth in  claim 3 , wherein a composition ratio of the CoFeSiB target is Co x Fe y Si 15 B 10  (atomic percent) where x=70.5˜75 and y=4.5˜0. 
     
     
       5. The method as set forth in  claim 3 , wherein the CoFeSiB—Pd alloy thin film is deposited under an atmosphere of argon and an atmosphere of 1 mTorr to 10 mTorr. 
     
     
       6. The method as set forth in  claim 1 , wherein a volume ratio of CoFeSiB to Pd is 1:1.6 to 1:7. 
     
     
       7. The method as set forth in  claim 1 , wherein a squareness of the CoFeSiB—Pd alloy thin film exhibiting the perpendicular magnetic anisotropy is 90 percent or more,
 saturation magnetization of the CoFeSiB—Pd alloy thin film is 200 emu/cm 3  or more, and 
 magnetic anisotropy energy is 1.53×10 6  erg/cm 3  or more. 
 
     
     
       8. A method to form a CoSiB—Pd alloy thin film exhibiting perpendicular magnetic anisotropy, the method comprising:
 simultaneously sputtering a CoSiB target and a Pd target inside a vacuum chamber to form a CoSiB—Pd alloy thin film of an amorphous structure without exhibiting perpendicular magnetic anisotropy on a substrate disposed inside the vacuum chamber; and 
 annealing the substrate, on which the CoSiB alloy thin film of an amorphous structure without exhibiting perpendicular magnetic anisotropy is formed, to change from the amorphous structure to a polycrystalline structure for exhibiting perpendicular magnetic anisotropy; 
 wherein the method further comprises forming a buffer layer before forming the CoSiB—Pd alloy thin film and forming a seed layer before forming the buffer layer, wherein the buffer layer is Pd having a thickness of 3 nm or more, wherein a temperature of annealing the substrate, on which the CoSiB—Pd alloy thin film is formed, is higher than 300 degrees Celsius and lower than 600 degrees Celsius, and wherein an interdiffusion of Pd elements occurs between the CoFeSiB—Pd alloy thin film and the buffer layer during the annealing. 
 
     
     
       9. The method as set forth in  claim 8 , further comprising:
 forming a capping layer after forming the CoSiB—Pd alloy thin film. 
 
     
     
       10. The method as set forth in  claim 8 , wherein the CoSiB—Pd alloy thin film is formed by dc sputtering using the CoFeSiB target and the Pd target. 
     
     
       11. The method as set forth in  claim 10 , wherein a composition ratio of the CoSiB target is Co 75 Si 15 B 10  (atomic percent). 
     
     
       12. The method as set forth in  claim 10 , wherein the CoSiB—Pd alloy thin film is deposited under an atmosphere of argon and an atmosphere of 1 mTorr to 10 mTorr. 
     
     
       13. The method as set forth in  claim 8 , wherein a volume ratio of CoSiB to Pd is 1:1.6 to 1:7.